A pulse oximeter is now widely used to obtain percutaneous oxygen saturation in arterial blood (SpO_2) continuously and noninvasively not only in the operating theater but also in the intensive care unit. Under general anesthesia there is no serious problem to obtain accurate SpO_2 because patients are not able to move spontaneously. However, in patients who can move by themselves in the intensive care unit, there are a lot of factors that can influence the measurement of SpO_2. There is the possibility that the pulse oximeter is influenced by the patients' body movement and the surrounding environment. In this study we have evaluated the influence of patients' body movement on the monitoring of SpO_2 in the intensive care unit. We used three different pulse oximeters, Symphony N-3000 (Nellcor Co., California, U.S.A), Biox 3740 (Ohmeda Co., Colorado, U.S.A) and SATLITE trans (DATEX Co., Helsinki, Finland). Although the SpO_2 value changed with the patient's body movement in all pulse oximeters, there were marked differences of the SpO_2 values among the three pulse oximeters. As for the reliability of the pulse oximeters, it was clear that there were marked differences of the SpO_2 values among the apparatuses with patients' body movement, more reliable analysis is needed.
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